The present invention relates in general to systems for removing contaminants from flue gases using a reagent and, in particular, to a new and useful system for removing SO.sub.2, NO.sub.2, and other contaminants from flue gases using hydrogen peroxide (H.sub.2 O.sub.2) as the reagent.
The flue gas produced during fossil fuel combustion and metallurgical ore refining is responsible for a significant portion of the SO.sub.2 emitted to the atmosphere. When gaseous SO.sub.2 combines with liquid water, a dilute aqueous solution of sulfurous acid (H.sub.2 SO.sub.3) is produced. Sulfurous acid readily oxidizes in the atmosphere to sulfuric acid (H.sub.2 SO.sub.4) which, together with nitric acid (HNO.sub.3), comprises the major acidic constituents of acid rain. Acid rain has caused considerable damage to lakes and forests in the Northeastern portion of North America and in the Black Forest region of Europe.
Legislative action has been responsible for most industrial SO.sub.2 controls and a variety of SO.sub.2 control processes and technologies have been developed in response thereto. Commercialized processes include wet, semi-dry (slurry spray with drying) and completely dry processes. Of these, the wet SO.sub.2 scrubber has been the dominant worldwide technology to control SO.sub.2 emissions from utility power plants; dry flue gas desulfurization (FGD) plants have also played a significant role.
Certain disadvantages are present in such commercially available FGD systems. The disposal of reaction products is still a concern in both wet and dry FGD systems. Power consumption requirements are significant, both to grind and prepare the reagent materials and to spray same into the flue gas. Many pieces of equipment are involved in such systems and the erosive properties of the reagent, such as limestone or lime, result in periodic maintenance and replacement of many components. While both wet and dry scrubber systems can achieve adequate SO.sub.2 removal efficiencies, high ratios of reagent to gas flow are often required.
The use of hydrogen peroxide to desulfurize flue gas is well known in the art. Commercially feasible installations are not commonplace for a variety of reasons.